Sound producer and receiver



Aug. 7, 1923. 1,463,911

w. RUDOLPH SOUND PRODUCER AND RECEIVER Filed Aug. 14 ,1920

Patented Aug. 7, 1923.

WILHELM RUDOLPH, OF KIEL, GERMANY, ASSIGNOR TO FIRM SIGNAL GESELLSCHAFTPATENT orrica.

M. B. H., OF KIEL, GERMANY.

SOUND PRODUCER/AND RECEIVER.

Application filed August 14, 1920. \Serial No. 403,542.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L.,1313.)

To all whomit may concern Be it knpwnjhatfll, WILHEL'M RUDOLPH, acitizen of the German Republic, and re- Sldlllg at Kiel, county ofSchleswig-Holstein, State of Prussia, Germany, have invented certain newand useful Improvements in Sound Producers and Receivers (for which Ihave filed a plications in Germany on March 9 1916, atent No. 299,130;in Denmark on ay 2, 1919, Patent No. 28,212; in Sweden on May 14, 1919;in Norway on May 15, 1919', Patent No. 36,540; in'

Holland on June 16, 1919, and July 3, 1920; in England on June 9 1920,Patent No. 144,673; in Belgium onduly 8, 1920, Patent No. 288,994; inSpain on July 7, 1920-; in France on July 8, 1920, Patent No. 532,119;and in Italy on July 9, 1920, Patent No. 541/246), of which thefollowing is a specification.

In emitting sound waves into different mediums or in taking in orreceiving these waves from these mediums the most favorable amplitude ofmotion that the body or structure (radiating member) which operates topass on the energy can execute depends on the degree of compressibilityof the particular medium in question. In cases in which the soundcollecting or radiating member abuts on liquids for instance, smallamplitudes of motion of the radiating member will suffice to produceconsiderable amplitudes of pressure, but to produce similar resultswhere the abutting medium is a gas, large amplitudes of motion arerequired. On the other hand the proper amplitudes of motion to selectfor the actual exciter of the sound waves, such as the working partsactuated by the electromagnet 1n electromagnetic sound producers, or forthe actual receiver, which may consist of a m crophone in a receivingapparatus, are entirely different. Hence it isnearly always necessary insound signalling apparatus of this kind to transform the amplitudes ofthe motions transferred from onevpoint of the apparatusto another. I

A known means of obtaining a transformation of the amplitudes consistsin interposing a separate vibratory body or stru ture between the art ofthe'sound signa ling apparatus t at abuts on the sound propagatingmedium, and the sound exciter or detector proper, and in attaching thesaid part and the exciter (or detector) to points of the said vibratorystructure which execute amplitudes of motion of different magnitudes.Another known feature conslsts in making such vibratory structures ofmembers whose various parts vibrate s mmetrically to an axis of theapparatus. ut as the sound exciter or detector was invariably attachedto a single point of the interposed member, and the sound collecting orradiating part of the apparatus likewise, it Was necessary to adopteither an unsymmetrical point of attachment or a point lymg on the axisof symmetry. If the former plan is adopted the vibrations of theinterposed vibratory structure will be unsymmetrical, and instead ofonly one natural rate of vibration it will have several, whereas if thesecond plan is chosen the number of the points of coupling open toselection is extremely small, it only being possible to connect thedifferent parts to certain very definite points of theinterposedstructure so thatgenerally speaking the ratio oftransformation of the amplitudes can-only be altered by changing thesize of the vibratory structure. But'as other factors are also to beconsidered in determining this size it will often be impossible tocomply with all the re uirements at the same time.

n accordance with the invention these difficulties are overcome byeffecting the coupling or attachment between the part of the soundsignalling apparatus that abuts on the sound propagating medium and thevibratory structure that operates to transform the amplitudes, at two ormore points which are symmetrical with respect to the nodal point orpoints (or line or lines) of the said structure. By this arrangement themeasurements of the vibratory structure and the radiating member arerendered a matter of indifference as far as the ratio of transformationis concerned and they can therefore be determined according to otherimportant and entirely different points of view. 4

The simplest practical solution of the problem is presented by insertingbetween the interposed vibratory structure and the other part or partsof the apparatus a rigid coupling member or members in the shape of afork or two forks to whose stem (or stems) and prongs the said otherparts are coupled. t each junction between the prongs and the saidvibratory structure the parts are joined through a point or line, forexample, by tapering the prongs to a point or to a knife-like edge, inorder that the prongs will not affect the vibratory structure in anundesired manner. These prongs may be pivoted to the-vibratory structure(for lowfrequen'cy vibrations), or they may (in all cases) be solderedthereto. When soldered it is particularly desirable to sharpen or notchthe prongs in order to permit them to bend and thus avert an undesiredinfluence on the vibratory structure.

Some constructional forms of the invention are illustrated in thedrawing in which Fig. 1 shows a coupling device consisting of two rigidcoupling forks associated with an elastic vibratory body or structure inthe form of a straight bar. Fig. 2 illustrates an arrangement in whichthe vibratory structure has the shape of a tuning fork, whereas in Fig.3 the interposed vibratory structure consists of a diaphragm.

Fig. 4 represents an arrangement with an interposed vibratory structurein the form of a ring and Figv 5 shows a device with a vibratorystructure composed of a ribbed band.

The arrangement of Fig. 1 comprises an interposed vibratory body in theform of an elastic bar 03 which is held firmly at the middle e. Its twohalves vibrate symmetrically with respect to the axis aa as indicated bythe broken lines. The ends of the bar d are the points of largestamplitude, the amplitudes decreasing continuously from the ends to themiddle 6. The points of attachment or coupling are arranged in pairs,the two points of each pair being symmetrical with respect to the axiso-o. Thus the points I) and 5, which execute small amplitudes of motionand exert great forces and the points 0 and c of large amplitudes andsmall forces, are pairs of coordinated points; and are connected to eachother in a manner suitable for the particular purpose in view by beams sand t which are perfectly still or rigid, or in other words whose tuningor natural rate of vibration is so much higher than the pitch of t issounds to be sent or received by the apparatus that they may be regardedas being per tectly rigid. Hence every point of the beam 8 executes thesame amplitudes of motion as the points of coupling 0, 0 and all pointsof the beam 5 execute the same amplitudes as the points Z), b,.According to the required ratio of the trans formation of the amplitudesof motion a sound exciter or detector would be connected to the one beamand a sound radiating or collecting member to the other.

In Fig. 2 the interposed elastic vibratory structure has the form of atuning "fork g.

The axis of symmetry of the vibrations is the line (Ir-a1. The points oflargest amplitude are c, 0 whilst the nodal points lie at 6, 6 Inaccordance with the invention the coupling is effected at two pairs ofpoints that are symmetrical to the axis and are at the desired distancefrom the nodal points. In the example illustrated this is accomplishedby connecting the points b, b, by a rigid beam or fork t, or in otherwords a fork of a very high sound pitch, and by mounting the fork on thesound radiating surface, as on the hull w of a ship.

In Fig. 3 the interposed elastic vibratory structure is made in the formof :1 diaphragm m which is held firmly in a ring with its vibratingparts symmetrical to the axis a--a. This diaphragm is, coupled at thepoints 6, b, (which are situated symmetric-ally with respect to the saidaxis) to the centre of a diaphragm M that abuts on the sound propagatingmedium, the coupling being effected by a rigid bent beam or fork t. Inthis instance the coupling points 0, c of Fig. 1, i. e. the points thatexecute the largest amplitudes, are united in one point 0 situated inthe axis of symmetry. in this case the preferred plan would be to use alarger number of symmetrically situated coupling points lying on aconcentric circle, instead of only. a pair or such points. The point 0is connected to a. sound exciter or detector f.

In Fig. 4 a ring acts as an elastic interposed vibratory member. e, e,e", 0 denote its nodal or motionless points. In accordance with theprocedure hereinbefore described the coupling is effected at a pair ofpoints 5, b, that lie symmetrical with respect to one of the axes ofsymmetry. Here again the points b, b may be interconnected by a rigidbeam t and joined to the sound emitting or collecting hull w of a ship,while a sound exciter or detector is applied at the point 0.

In all the cases dealt with so far it was assumed that the frequency ofthe sound exc ter or of the arriving sound waves concided with the pitchof the independent interposed vibratory structure. But the in* ventionis not limited to such special cases for, if a suitable form ofvibratory structure is chosen, it will enable the amplitudes of soundWaves of any frequency and character to betransformed. A case in pointis shown in Fig. 5 in which (Z is a band or bar of a very low rate ofvibration firmly fixed at both ends. In order that the bar d may only beable to oscillate as a whole it is equipped at both sides with ribs131'. The axis of symmetry of its vibrations is (1-11.. The pair ofcoupling points situated symmetrically with respect to the said axis isb, b. Instead of coupling the exciter or detector at c any pair ofpoints may be selected for this purpose as long as they lie symmetricalto the axis a-a.

Instead of a bar as shown in Fig. 5 a diaphragm stiffened by radial ribsmay be em ployed. The pair of points I), 6' could then be replaced byany number of coupling points situated on a circle concentric to theaxis of symmetry. The coupling point 0 could be left on the axis ofsymmetry or could be resolved into a number of points lying on aconcentric circle around the axis of symmetry.

The ratio of the transformation of the amplitudes need not beunchangeable, for the arrangementmay be such that the distance betweenthe pairs or groups of coupling points and the nodal points is capableof being continuously altered.

It is to be understood that the term radiating member as used in theclaims designates any member which receives vibrations from the soundpropagating medium and radiates them to another member or structure, orrec'eives vibrations from another member or structure and radiates themto the s6und propagatin medium. the term refers to both senders andreceivers.

I claim:

1. In a device for transferring sound vibrations, a radiating member, astructure capable of executing independent vibrations, and meansattached to said radiating member and adapted to transmit vibrationsbetween said radiating member and said vibratory structure, said meansengaging the latter at points on opposite sides of and equidistant fromthe axis of symmetry of vibrations of the latter.

2. In a device for transferring sound vibrations, a radiating member, astructure capable of executing independent vibrations, and a forkedmember having its stem attached to said radiatin member and adapted totransmit vibrations etween said radiating member and said vibratorystructure, the prongs of said forked member engaging the vibratorystructure at points on opposite sides of and equidistant from the axisof symmetry of vibrations of the latter.

3. In a device for transferring sound vibrations, a radiating member, astructure capable of executing independent vibrations, and meansattached to said radiating member and adapted to transmit vibrationsbetween said radiating member and said vibratory structure, said meansengaging the latter at points each of which is equidlstant from a nodalpoint of the latter.

Thus

4. In a.- device for transferring sound vibrations, a radiating member,a diaphragm capable of executing independent vibrations, and meansattached to said radiating member and adapted to transmit vibrationsbetween said radiating member and said diaphragm, said means engagingthe latter at diametrically opposite points each of which is equidistantfrom a nodal point of the latter.

5. In a device for transferring sound vibrations, a radiating member, astructure capable of executing independent vibrations and having point-sthereof adapted to execute vibrations of relatively small amplitude andother points adapted to execute vibrations of relatively largeamplitude, and means attached to said radiating member and ada ted totransmit vibrations between said ra iating member and said vibratorystructure, said means engaging the vibratory structure at points thereonhaving a relativel .small amplitude of vibration and each 0 which isequidistant from a nodal point of the vibratory structure.

6. In a device for transferring sound vibrations, a radiating member, astructure capable of executing independent vibrations and having pointsthereof adapted to execute vibrations of relatively small amplitude andother points adapted to execute vibrations of relatively largeamplitude, and means attached to said radiating member and adapted totransmit vibrations between said radiating member and'said vibratorystructure, said means engaging the vibratory structure at points thereonhaving a relatively small amplitude of vibration and located on oppositesides of and equidistant from the axis of symmetry of vibrations of thevibratory structure.

7. In a device for transferring sound waves, a radiating member, avibratory structure, energy-converting means connected to said vibratorystructure, and means interconnecting the radiating member and thevibratory structure at a plurality of points on the latter in suchmanner that these points are situated symmetricall to the axis ofsymmetry of vibrations o the vibratory structure and that the vibratorystructure and the interconnecting means are adapted to transform theamplitudes of vibrations passing betweenthe radiating mem ber and theenergy-converting means so that the amplitude of the vibrations at theradiating member is different from the amplitude at theenergy-converting means.

8. A device according to claim 2, in which the forked member has anatural rate of vibration higher than that of the sounds to betransferred, so that it does not execute natural vibrations during thetransference.

9. A device according to claim 2, in which the prongs of the forkedmember are sharp at the point of engagement with the vibratorystructure.

10. In a device for transferrin sound waves, a radiating member, avibratory structure in the form of a diaphragm, energy-converting meansconnected to said vibratory structure, and means interconnecting theradiating member and the vibratory structure at a plurality of points onthe latter in such manner that these points are situated symmetricallyto the axis of symmetry of vibrations of the vibratory structure andthat the vibratory structure and the interconnectin means are adapted totrans form the amp 'tudes of vibrations passing between theradiatingmember and the energy-c0nverting means so that the amplitude ofthe vibrations at the radiating member is different from the amplitudeat the energyconvertmg means In testimony whereof I affix my signaturein presence of two witnesses.

. WILHELM RUDOLPH.

Witnesses: WALTER HALMEMANN, ALORD DU' BOIS RAYMOND.

